An activator of the type with which the invention is concerned is already known, namely urokinase, which is extracted from the urine of mammals (cf. U.S. Pat. Nos. 2,961,382; 2,983,647 and 2,989,440). However, it has been found that urokinase is very sensitive to induced inhibitors and that its effect diminishes very quickly.
Accordingly, there is a need for an activator which is at least equivalent to urokinase in regard to activity, but which is unaffected by inhibitors.